I have used this company on several excursions in the Caribbean and am signed up for two more on our cruise next week. Alot of times they give times in local time. So what appears to be a one hour window may in fact be two. Just e-mail them from their site and ask. They are happy to help you. (Really) I have found that because most of their business relies on word of mouth and repeat customers, they are overly cautious to get you back to the ship on time.
I found the excursions through this company on the advice of my travel agent, and boy was she right! The groups are smaller and more personal and usually offer more for the same amount as the cruise line. For example, we are going to the Chacchoben ruins in Costa Maya next week with them. Our guide is a native who actually lived in the ruins as a child, and has a special love and knowledge of them. Then he will be taking us to a local family to have a native lunch. (no fresh fruit, bring water with you due to the GI problems that can occur) In the last two weeks, Joanne from Shoretrips has called me twice! Once to make sure I had sucessfully printed my vouchers and to give me a phone number to call if I had any problems. The second time was to let me know to reprint the Costa Maya voucher because there were new contact directions. SHE CALLED ME! She didn't just throw out an e-mail and hope I got it. Amazing!
I can't recommend this company more highly and wouldn't question that they are just as interested as you are to get you back to the ship in time. They welcome as many questions as you need to ask by e-mail or phone before you buy, so ask to make sure. They really do have their stuff down!